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68132b3536
- Fix long standing lockdep issue of using remap_pfn_range() from
the vfio-pci fault handler for mapping device MMIO. Commit
ba168b52bf8e ("mm: use rwsem assertion macros for mmap_lock") now
exposes this as a warning forcing this to be addressed.
remap_pfn_range() was used here to efficiently map the entire vma,
but it really never should have been used in the fault handler and
doesn't handle concurrency, which introduced complex locking. We
also needed to track vmas mapping the device memory in order to zap
those vmas when the memory is disabled resulting in a vma list.
Instead of all that mess, setup an address space on the device fd
such that we can use unmap_mapping_range() for zapping to avoid
the tracking overhead and use the standard vmf_insert_pfn() to
insert mappings on fault. For now we'll iterate the vma and
opportunistically try to insert mappings for the entire vma. This
aligns with typical use cases, but hopefully in the future we can
drop the iterative approach and make use of huge_fault instead,
once vmf_insert_pfn{pud,pmd}() learn to handle pfnmaps.
(Alex Williamson)
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Merge tag 'vfio-v6.10-rc4' of https://github.com/awilliam/linux-vfio
Pull VFIO fixes from Alex Williamson:
"Fix long standing lockdep issue of using remap_pfn_range() from the
vfio-pci fault handler for mapping device MMIO. Commit ba168b52bf8e
("mm: use rwsem assertion macros for mmap_lock") now exposes this as a
warning forcing this to be addressed.
remap_pfn_range() was used here to efficiently map the entire vma, but
it really never should have been used in the fault handler and doesn't
handle concurrency, which introduced complex locking. We also needed
to track vmas mapping the device memory in order to zap those vmas
when the memory is disabled resulting in a vma list.
Instead of all that mess, setup an address space on the device fd
such that we can use unmap_mapping_range() for zapping to avoid the
tracking overhead and use the standard vmf_insert_pfn() to insert
mappings on fault.
For now we'll iterate the vma and opportunistically try to insert
mappings for the entire vma. This aligns with typical use cases, but
hopefully in the future we can drop the iterative approach and make
use of huge_fault instead, once vmf_insert_pfn{pud,pmd}() learn to
handle pfnmaps"
* tag 'vfio-v6.10-rc4' of https://github.com/awilliam/linux-vfio:
vfio/pci: Insert full vma on mmap'd MMIO fault
vfio/pci: Use unmap_mapping_range()
vfio: Create vfio_fs_type with inode per device
Linux kernel
============
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